Commutator resurfacer



Patented Feb. 28, 1928.

UNITED STATES JOHN WALTER BECKER, or CHICAGO, ILLINOIS.

COMMUTATOB RESURFACER.

No Drawing.

This invention relates to commutator resurfacers for resurfacing the commutators and collector rings of electric machines. When electric machines having commutators such as generators, rotary converters, motors and the like are used the commutators be come worn and uneven due to the rubbing of the brushes thereon and sparking and flashing.

It is necessary to resurface these commutators at intervals in order to maintain the efficiency of the machine. The object of my present invention is to provide a new and improved commutator resurfacer which can be easily and cheaply made, and which has a high efliciency and which cuts rapidly and. does not fill up with the-metal removed from the commutator.

My present device may be used while the electrical machine is in service. If the metal of the commutator should adhere to the resurfacer, it would short circuit the commutator sections and injure and burn out the armature. With my device this difiiculty is entirely eliminated.

In carrying out my invention I form a block of the material of the desired size so that it can be pressed upon the commutator while the commutator is rotated so as to resurface it and-form a smooth exterior surface thereon. In making up this block I use certain materials as for example an abrading material' in a finely divided state, a suitable adhesive binder material, and a material which when the mass is heated will evaporate or substantially disappear so as to leavea "porous or honeycombed mass. In the,preferred form I also add a material which decreases or destroys adhesiveness of the binder so as to cause the block to break down or wear down readily when used and to do this without adhesive qualities so that the metal of the commutator will not adhere 0 the block to short circuit the commutator ars.

It is of course evident that various materials may be used but I find that good results, and in fact the best results is secured by using the following materials.

I preferably use for the abrading material aluminum oxide in a crystalline state such as alundum or aloxide. For the adhesive material I may use shellac. For the material for producing a porous honeycomb condition I may use resin. For the material for destroying or decreasing the adhesiveness of Application filed December a0, 1918. Serial No. 268,966.

the adhesive binder I may use sawdust in a finely divided form. I prefer to use hard wood sawdust.

The proportions of the materials may be yaricd. If for example I use aluminum oxide in a crystalline form, shellac and resin alone, I may use the proportions by weight of severity-five parts aluminum oxide, eight parts of shellac and one part of resin. If I use the aluminumoxide, shellac, resin and sawdust which secures the preferred and best results I may use by weight say two hundred parts of aluminum oxide, fifteen parts of shellac, three parts of resin and one part of sawdust.

The materials may be mixed in various ways. I prefer to mix all the materials while in a dry state and then heat them, the materials being stirred while being heated, whereupon they soften into a mass. This mass is then molded into blocks and baked. The material, however, can be mixed by first reducing the shellac in liquid state by heating it or diluting it with alcohol and mixing the other materials in a dry state adding the shellac and then forming into blocks and baking. The heat used in baking the blocks is of a comparatively low temperature say 200 or 300 degrees Fahrenheit. The sawdust greatly facilitates the making of theblocks and produces a superior product.

When the block is made it is then ready for use and may be applied to the commutator of the electric machine, while the machine is in operation. The block either with or without a holding. device is pressed upon the commutator while the commutator is rotating and resurfaces it cutting away the material so as to remove the rough and un- .I

even portions. The material of the block breaks down readily without adhesive qualities so that the metal cut away does not adhere to the surface of the block and hence no short circuiting of the commutator sections occurs. The resurfacing of the commutator may be accomplished while the machine is still in active service.

This resurfacer does not drag the particles of copper, removed from the commutator bars, across the mica insulating pieces between such bars, and there is therefore no possibility of short circuits, and the mica insulating pieces are also properly smoothed and left without grooves or roughness.

I claim 1. A resurfacing device for the commutators of electric machines comprising two hundred parts by weight of aluminum oxide, fifteen parts by weight of shellac, three parts by weight of resin, and one part by weight of sawdust, said material being thoroughly mixed.

4. A resurfacing device for the commutators of electric machines comprising a block made up of abrading material in a finely divided state formed into a porous honeycombed mass with sawdust distributed therethrough, whereby the material readily breaks down when used on a commutator so that the metal of the commutator does not adhere to the block to short circuit the commutator bars.

5. A resurfacing device for commutators of electric machines comprising a block of abrading material in a finely divided state,'

and formed into a porous structure, an abrasive binder for holding said abrading material together, and means for decreasing the adhesiveness of the binder so as to cause the block to wear down readily without causing the metal removed from the commutator to adhere thereto to produce a short circuit between the commutator bars.

In testimony whereof, I aflix my signature this 21st day of December, 1918.

7 JOHN WALTER BECKER. 

